JP3688791B2 - Pneumatic radial tire - Google Patents

Description

【００３２】
表１の結果から、実施例Ａ，Ｂは、それぞれ従来例Ａ，Ｂに比べ、乾燥路面での操縦安定性は同等であり、排水性が向上している。
【００３３】
【発明の効果】
本発明によれば、溝容積を増加させないで排水性を向上させることができるので、乾燥路面での操縦安定性も十分に確保することができる。
従って、本発明によって、従来、二律背反する関係にあると考えられていた、濡れた路面での排水性と乾燥路面での操縦安定性との双方を満足させることが可能になった。
【図面の簡単な説明】
【図１】本発明に従う代表的な空気入りラジアルタイヤのトレッドパターンを示す図である。
【図２】従来タイヤ（横溝の配設角度θが90°）のトレッドパターンを示す図である。
【図３】従来タイヤ（横溝の配設角度θが120 °）のトレッドパターンを示す図である。
【図４】従来タイヤ（横溝の配設角度θが 135°）のトレッドパターンを示す図である。
【図５】従来タイヤ（横溝の配設角度θが 150°）のトレッドパターンを示す図である。
【図６】種々の因子を変化させて、横溝の配設角度θに対するハイドロプレーニング発生速度の値をプロットした図である。
【図７】 (a) は本発明に従う空気入りラジアルタイヤの他のトレッドパターンを示す図であり、
(b) は従来タイヤである。
【図８】 (a) は本発明に従う空気入りラジアルタイヤの他のトレッドパターンを示す図であり、
(b) は従来タイヤである。
【符号の説明】
1 トレッド部
2 円周主溝
3 トレッド端
4 横溝
5 ブロック陸部
5a 一方の角部( ブロック陸部５の後続接地する側に角部)
5b 他方の角部( ブロック陸部５の後続接地する側に角部）
6 タイヤの回転方向
7 タイヤ赤道
8 トレッド中央域
9,10 トレッド側方域
11 車両外側
12 車両内側
13 傾斜溝
14 傾斜溝13と円周主溝2b又は2cの連通位置
15 横溝4a又は4bの分岐位置[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a pneumatic radial tire having both good steering stability on a dry road surface and sufficient drainage on a wet road surface.
[0002]
[Prior art]
Generally, the main functions of the pattern applied to the tread of a pneumatic tire include the provision of design to the tire appearance and the securing of drainability when traveling on wet road surfaces. In consideration of the above, various patterns have been developed according to applications.
[0003]
Examples of the arrangement groove constituting the tread pattern include a circumferential main groove extending along the tire circumference and a lateral groove extending from the circumferential main groove and extending in the tread end direction. The tire that has the water drainage is secured by discharging the water that has entered the tire contact area from the circumferential main groove to the side of the tire through the lateral groove (particularly the side of the tire located outside the vehicle).
[0004]
In order to improve the drainage performance of the tire, it is easiest to increase the groove volume of the arrangement groove. However, if the groove volume is increased, the steering stability on the dry road surface is deteriorated. For tires with a pattern, it has been difficult to achieve both drainage on wet roads and steering stability on dry roads.
[0005]
[Problems to be solved by the invention]
Accordingly, the object of the present invention is to improve the shape of the groove of the arrangement groove, specifically, the corner shape of the block land portion without increasing the groove volume of the arrangement groove, so that it is good on a dry road surface. It is an object of the present invention to provide a pneumatic radial tire having excellent steering stability and sufficient drainage on wet road surfaces.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, a pneumatic radial tire according to the present invention includes a plurality of circumferential main grooves extending along a tire circumference at a tread portion, a branch from the circumferential main groove, and a tread end. The circumferential main groove located on the side or a plurality of lateral grooves extending to communicate with the tread end are provided to form a plurality of block land portions, and at least in the vehicle mounting posture of the tire, In the block land portion located in the tread side area outside the vehicle, it is formed by a circumferential main groove and a lateral groove branched from this and extending toward the tread end, and subsequently grounded. only one corner, the angle θ is an angle of 90 ° ~ 135 °, and in that the radius of curvature R is concerned with the formation as round becomes R ≧ d and the width d of the lateral groove. When this tire is used, the one corner of the block land portion located at least in the tread side region outside the vehicle among the two tread side regions is subsequently grounded to the other corner portion. It is necessary to install the tire on the vehicle. Further, the tread side area referred to here means an area on both sides when the tread ends are equally divided into three, and an area sandwiched between the areas on both sides is called a tread central area.
[0007]
In addition, the block land portion referred to here is a land portion formed by dividing the tire circumference into two transverse grooves and two circumferential main grooves arranged at intervals to separate the tire circumference (Fig. 8 ( In addition to 5-1) of a), the land portion formed by dividing the two lateral grooves, one of the circumferential main grooves and the tread end (reference 5-2 in FIG. 8 (a)). ) Is also included. In addition, the numerical value of the angle θ of one corner is assumed to be a corner when the corner is not rounded, and the larger one of the angles formed by the circumferential main groove and the lateral groove in this case Asking for the same.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows a part of a typical tread portion of a pneumatic radial tire according to the present invention, in which 1 is a tread portion, 2 is a circumferential main groove, 3 is a tread end, 4 is a lateral groove, and 5 is a block. The land, 5a and 5b are the corners of the block land.
The pneumatic radial tire of this figure has a plurality of circumferential main grooves 2 extending along the tire circumference in the tread portion 1 and a plurality of branches extending from the circumferential main groove 2 until they communicate with the tread end 3. A plurality of block land portions 5 are defined in the tread portion 1 by arranging the horizontal grooves 4 of the books.
[0010]
Of the two corners 5a, 5b of the block land 5 formed by the circumferential main groove 2 and the lateral groove 4 branched from this, the angle θ of one corner 5b is set to 90 ° to 135 ° (FIG. 1). In the range of 90 °), and the corner 5b is rounded. By adopting such a configuration, the pneumatic radial tire of the present invention can improve drainage.
[0011]
In addition, it is discovered from the test result which the inventor performed below that there exists an improvement effect of drainage by employ | adopting such a structure.
[0012]
(Test 1)
First, in order to clarify the change in drainage due to the arrangement angle θ of the horizontal groove 4 branched from the circumferential main groove 2, the larger arrangement angle θ (θ is the larger angle between the circumferential main groove and the horizontal groove). This means the angle, specifically the angle of the corner 5b on the side of the block land that comes into contact with the ground.) Was changed in four steps (Figures 2 to 5) in the range of 90 ° to 150 °. The quality of drainage was investigated. Drainage performance was evaluated by measuring the minimum speed at which hydroplaning occurs (hereinafter referred to as “hydroplaning generation speed”) when running on a road surface with a puddle with a water depth of 10 mm. In addition, drainage property is so excellent that the hydroplaning generation | occurrence | production speed | rate is large. 2 shows a case where the arrangement angle θ is 90 °, FIG. 3 shows a case where the arrangement angle θ is 120 °, FIG. 4 shows a case where the arrangement angle θ is 135 °, and FIG. This is a tread pattern when the installation angle θ is 150 °. For pneumatic radial tires having these tread patterns, the relationship between the lateral groove arrangement angle θ and the hydroplaning generation speed (km / h) is shown in FIG. 6 (circles on the solid line in the figure). From this figure, it was found that the hydroplaning generation speed increases as the lateral groove arrangement angle θ increases.
[0013]
(Test 2)
Next, in order to clarify whether or not the drainage performance is changed by rounding the two corners 5a and 5b of the block land portion 5, the tire having the tread pattern shown in FIG. θ was 90 °), and the hydroplaning generation speed when one of the two corner portions 5a and 5b of the block land portion was rounded was examined. The results are plotted in FIG. 6 (in the figure, the hydroplaning generation speed is shown as an index ratio with the conventional tire shown in FIG. 2 as 100), but the other corner 5a of the block land 5 (specifically The speed of hydroplaning of a tire with rounded corners (in the figure, the corner on the side that precedes the ground contact) is the same as the speed of hydroplaning of tires without rounding. However, a tire with a rounded corner 5b (specifically, a corner on the side where the block comes into contact with the ground) of the block land is rounded. The hydroplaning rate increased compared to the tires without, and drainage performance was improved.
[0014]
(Test 3)
Furthermore, in order to clarify whether or not the drainage improvement effect by rounding the one corner 5b of the block land portion 5 is different depending on the difference in the arrangement angle θ of the lateral groove, FIG. The hydroplaning generation speed when the tire having the tread pattern shown in FIG. 5 was rounded at one corner 5b of each block land portion was measured. The result is also plotted in FIG. 6 (indicated by □ in the figure). From this result, it is determined whether or not one corner 5b of the block land portion is rounded when the arrangement angle θ exceeds 135 °. Regardless, the drainage is good due to the effect of the horizontal groove arrangement angle (however, in this case, the angle of the other corner 5a of the block land is quite acute, so other performance such as uneven wear) Therefore, the drainage improvement effect by rounding the corner 5b is not recognized. On the other hand, when the arrangement angle θ is less than 90 °, it is not possible to enter the contact area sequentially from the branch portion of the lateral groove toward the tread end, and it is not possible to quickly discharge water to the side of the tire. Absent.
[0015]
Based on the above test results, the pneumatic radial tire of the present invention is one of the two corners 5a, 5b of the block land portion 5 formed by the circumferential main groove 2 and the lateral groove 4 branched therefrom. The angle θ of the corner portion 5b is in the range of 90 ° to 135 °, and the corner portion 5b is rounded.
[0016]
In addition, by rounding one corner 5b of the block land, the drainage improvement effect is obtained when the water that has entered the contact area flows into the lateral groove from the circumferential main groove 2 This is thought to be due to a reduction in energy loss at this branch.
[0017]
That is, when the case where the water that has entered the contact area is drained to the side of the tire through the circumferential main groove 2 and the lateral groove, the water that has flowed with directivity by the circumferential main groove 2 is In order to flow from the main groove to the horizontal groove, the direction must be changed at a steep angle, and when the one corner 5b of the block land 5 is not round and square like the conventional tire shown in FIG. The flow from the circumferential main groove to the horizontal groove does not go smoothly, and the energy collides with the corners of the block at the branching portion, resulting in a large loss of energy. Therefore, it was difficult to quickly drain the water that entered the tire contact area to the side of the tire.
[0018]
On the other hand, in the tire of the present invention, the corner portion 5b of the block land portion 5 is rounded, so that the flow of water from the circumferential main groove to the lateral groove only requires a gentle change of direction. The ratio of energy loss becomes smaller and the flow of water from the circumferential main groove to the lateral groove becomes smoother. As a result, the water that has entered the tire contact area passes through the circumferential main groove 2 and passes through the branch portion. Since it can pass relatively smoothly and flow into the lateral groove, the water that has flowed in can be quickly discharged to the side of the tire through the lateral groove with almost no energy loss.
[0019]
Further, in order to clarify whether the magnitude of the radius of curvature R affects drainage when the one corner 5b of the block land 5 is rounded, a tire having the tread pattern shown in FIG. (When the arrangement angle θ is 90 °), the curvature radius R when one corner 5b of the block land portion is rounded is changed with respect to the groove width d (d is constant). The hydroplaning generation rate in the case of (R = 0.5d, 1.0d, 1.3d) was investigated. This result is also plotted in FIG. 6. From this result, as the radius of curvature R of the roundness applied to one corner 5b of the block land portion is increased with respect to the groove width d of the horizontal groove, hydroplaning is performed. It can be seen that the generation rate is further increased and drainage performance is improved.
[0020]
Therefore, in the present invention, the radius of curvature R of one corner 5b of the block land portion 5 is set in relation to the groove width d of the lateral groove, specifically, R ≧ d , more preferably d. By making it into the range of ≦ R ≦ 1.3 d , the drainage performance is further improved.
[0021]
Moreover, when using the pneumatic radial tire of this invention, the direction to mount | wear to a vehicle is limited. That is, the tire is mounted on the vehicle so that at least one corner 5b of the block land 5 located in the tread side region 9 on the vehicle outer side 11 is grounded later than the other corner 5a. (FIG. 1).
[0022]
For example, as shown in FIG. 1, when the tread pattern is a symmetric (line symmetric) pattern centered on the tire equator 7, the tread pattern is in the tire rotation direction 6 shown in FIG. .1 on the condition that the one corner 5b of the block land 5 located at 10 is mounted on the vehicle so that it comes in contact with the ground more than the other corner 5a. As long as the tire is assembled to the rim, it may be mounted on either the right wheel or the left wheel.
[0023]
Further, in the case of a pneumatic radial tire having a point-symmetric pattern as shown in FIG. 8 (a), the one corner 5b of the block land portion 5-2 located in the tread side region 9 on the vehicle outer side 11 is provided. However, on the condition that the tire is mounted on the vehicle so as to make a subsequent contact with the other corner 5a, the tire rotation direction 6 shown in FIG. 8 (a) is limited to the left wheel. This is because the tread side area 10 is located on the outside of the vehicle when used for the right wheel in the case of the tire rotational direction 6 shown in FIG. In addition, since one corner 5b is grounded earlier than the other corner 5a, the remarkable effect of the present invention can be obtained by rounding one corner 5b. Because there is no.
[0024]
As another embodiment, as shown in FIG. 7 (a), one circumferential main groove 2a at the position of the tire equator 7 and one circumferential main groove 2b, 2c is arranged, and a plurality of transverse grooves 4a or 4b extending from the circumferential main groove 2b or 2c arranged in the lateral region 9 or 10 to extend to the tread end 3a or 3b are arranged. An inclined groove 13a or 13b that is steeply inclined in the region 8 and gently inclined toward the tread side region 9 or 10 is communicated with the circumferential main groove 2b or 2c arranged in the side region, and this communication position 14 is connected to the lateral groove 4a. Alternatively, in the case of a tire having a tread pattern in which one corner 5b of the block land 5 located in both sides 9 or 10 is made to coincide with the branch position 15 of 4b, the same effect as the tire shown in FIG. Play.
[0026]
The above description shows only some of the embodiments of the present invention, and various modifications can be made within the scope of the claims.
[0027]
【Example】
Next, two types of pneumatic radial tires A and B according to the present invention were prototyped and their performance was evaluated.
Example A
The pneumatic radial tire of Example A has a tread pattern as shown in FIG. 7 (a), the tire size is 225 / 50R16, one circumferential main groove 2a at the position of the tire equator 7, and both side regions 9 , 10 have a total of three circumferential main grooves 2b, 2c each, and branch from the circumferential main groove 2b or 2c disposed in the side region 9 or 10 to communicate with the tread end 3a or 3b. A plurality of horizontal grooves 4a or 4b extending to the tread side area 9 or 10 are further arranged, and an inclined groove 13 that is steeply inclined in the tread central area 8 and gently inclined toward the tread side area 9 or 10 is arranged in the side area 9 or 10. The circumferential main groove 2b or 2c is communicated, the communication position 14 is made to coincide with the branch position 15 of the lateral groove 4a or 4b, and the block land portion 5 located in the lateral region 9 or 10 The corner 5b was rounded with a radius of curvature R of 9 mm, which is 1.3 times the width d (7 mm) of the lateral grooves 4a and 4b.
The present invention is characterized by a tread portion, and a normal tire structure such as a carcass or a belt is used.
[0028]
Example B
The pneumatic radial tire of Example B has the tread pattern shown in FIG. 8 (a), the tire size is 225 / 50R16, two central main grooves 2a in the tread central region 8, and the side regions 9 on both sides. , 10 in total, each having four circumferential main grooves 2b, between the circumferential main groove 2a located in the tread central area 8 and the circumferential main groove 2b located in the side area 9 or 10, and Plural pieces extending from the respective circumferential main grooves 2a to the other circumferential main grooves 2b or the tread ends 3 between the circumferential main grooves 2b and the tread ends 3 located in the side regions 9 or 10 By arranging the horizontal grooves 4, four rows of block land portions are defined, and the corner portions 5 b on the side where the block land portions 5-1 or 5-2 are located at the center of the tread and are subsequently grounded In addition, a roundness having a radius of curvature R of 9 mm, which is 1.3 times the width d (7 mm) of the lateral groove 4, was applied.
The present invention is characterized by a tread portion, and a normal tire structure such as a carcass or a belt is used.
[0029]
・ Conventional examples A and B
In order to clarify that the inventive tire has excellent performance, for Example A, Conventional Example A (FIG. 7 (b)) having the same tire structure except that the corner 5b is not rounded is used. For Example B, performance evaluation was also performed as a comparison with Conventional Example B (FIG. 8 (b)) having the same tire structure except that the corner 5b was not rounded.
[0030]
(Test method)
Each of the above test tires was mounted on a vehicle and traveled on an actual vehicle. At this time, drainage performance on a wet road surface and steering stability on a dry road surface were evaluated.
The results are shown in Table 1. The numerical values of Examples A and B shown in Table 1 are shown as index ratios when the conventional examples A and B are set to 100, respectively. Both the drainage performance and the handling stability increase the performance. Is excellent.
[0031]
[Table 1]

[0032]
From the results of Table 1, Examples A and B have the same handling stability on the dry road surface and improved drainage compared to Conventional Examples A and B, respectively.
[0033]
【The invention's effect】
According to the present invention, the drainage performance can be improved without increasing the groove volume, and thus the steering stability on the dry road surface can be sufficiently ensured.
Therefore, according to the present invention, it has become possible to satisfy both the drainage performance on wet road surfaces and the handling stability on dry road surfaces, which are conventionally considered to be in a trade-off relationship.
[Brief description of the drawings]
FIG. 1 is a diagram showing a tread pattern of a typical pneumatic radial tire according to the present invention.
FIG. 2 is a view showing a tread pattern of a conventional tire (lateral groove arrangement angle θ is 90 °).
FIG. 3 is a diagram showing a tread pattern of a conventional tire (lateral groove arrangement angle θ is 120 °).
FIG. 4 is a view showing a tread pattern of a conventional tire (lateral groove arrangement angle θ is 135 °).
FIG. 5 is a view showing a tread pattern of a conventional tire (lateral groove arrangement angle θ is 150 °).
FIG. 6 is a graph plotting the value of the hydroplaning generation speed with respect to the lateral groove arrangement angle θ by changing various factors.
FIG. 7 (a) is a view showing another tread pattern of the pneumatic radial tire according to the present invention,
(b) is a conventional tire.
FIG. 8A is a diagram showing another tread pattern of a pneumatic radial tire according to the present invention,
(b) is a conventional tire.
[Explanation of symbols]
1 Tread
2 Circumferential groove
3 Tread edge
4 Horizontal groove
5 block land
5a One corner (corner on the side of the block land 5 that touches the ground)
5b The other corner (the corner on the side of the block land 5 where it touches the ground)
6 Tire rotation direction
7 tire equator
8 Central tread area
9,10 tread side area
11 Vehicle outside
12 Inside the vehicle
13 Inclined groove
14 Communication position of inclined groove 13 and circumferential main groove 2b or 2c
15 Branching position of lateral groove 4a or 4b

Claims (2)

A plurality of circumferential main grooves extending along the tire circumference and extending from the circumferential main groove to the tread portion until they communicate with the circumferential main groove or the tread end located on the tread end side. by disposing the lateral grooves of the plurality of the pneumatic radial tire ing to define a large number of block land portions,
Two corners formed by a circumferential main groove and a lateral groove extending from the circumferential main groove and extending toward the tread end of the block land portion located at least in the tread side region outside the vehicle in the vehicle mounting posture of the tire Only one of the corners that is grounded subsequently has an angle θ of 90 ° to 135 ° and a radius of curvature R that satisfies R ≧ d in relation to the width d of the lateral groove. rounded to pneumatic radial tire characterized by comprising a. 2. The pneumatic radial tire according to claim 1, wherein a radius of curvature of the one corner is in a range of d ≦ R ≦ 1.3 d in relation to a width d of the lateral groove .

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